A method detects a fault on a line of an electrical power supply system, in which current values are measured at the line ends of the line and the current values are used to check whether there is a fault on the line. In order to perform monitoring of the line such that faults can be detected comparatively quickly and sensitively, it is proposed that voltage values are also measured at the line ends. The respective measured current and voltage values are used to ascertain respective comparison current values indicating the current flowing at a comparison location on the line and the respective comparison current values are used to check for the presence of a fault on the line, and a fault signal is generated if the check has resulted in a fault present on the line being detected.

In a protective relay device, a current differential relay computation unit determines whether or not a fault has occurred within a protected section based on an operating quantity and a restraint quantity. A disconnection detection unit computes a first amount of difference by subtracting the operating quantity a certain time period ago from the operating quantity at a present point in time, computes a second amount of difference by subtracting the restraint quantity the certain time period ago from the restraint quantity at the present point in time, and determines that a disconnection has occurred at one of first and second current transformers when a first determination condition that an absolute value of a sum of the first amount of difference and the second amount of difference is equal to or smaller than a first set value is satisfied.

Transmission-line voltage measurements in a digital-electricity power system are validated by acquiring a series of transmission-line voltage measurements during a sample period when a transmitter-disconnect device is in a non-conducting state. A numerical analysis is performed to determine a point in time at which AC components in the transmission line have diminished and at which the primary change in the transmission-line voltage measurement values is due to DC decay. A receiver acquires a series of receiver-voltage measurements during the same sample period; and a numerical analysis is performed on the receiver-voltage measurements to determine the point in time at which the AC components have diminished and where the primary change in the transmission-line voltage measurement values is due to DC decay. The transmitter-disconnect device is then placed in a non-conducting state based on an evaluation of those measurements.

An over-current protection apparatus constituted of: a transistor disposed on a substrate; a first thermal sense device arranged to sense a temperature reflective of a junction temperature of the transistor; a second thermal sense device arranged to sense a temperature reflective of a temperature of a casing surrounding the substrate; and a control circuitry, arranged to alternately: responsive to the sensed temperature by the first thermal sense device and the sensed temperature of the second thermal sense device being indicative that the temperature difference between the transistor junction and the substrate casing is greater than a predetermined value, switch off the transistor; and responsive to the sensed temperature by the first thermal sense device and the sensed temperature by the second thermal sense device being indicative that the temperature difference between the transistor junction and the substrate casing is not greater than the predetermined value, switch on the transistor.

There is provided a method of operating a reconfigurable differential protection scheme for carrying out differential protection of an electrical power network, the electrical power network comprising terminals, each of the terminals configured to be in communication with each other within a communications network. The method includes controlling the differential protection scheme to deactivate the differential protection, and selecting a terminal to be configured out of or into the differential protection scheme. The method also includes communicating reconfiguration information among the terminals, the reconfiguration information including the selection of the terminal to be configured out of or into the differential protection scheme. The method also includes modifying a respective differential protection algorithm at each of the non-selected terminals so as to configure the selected terminal out of or into the differential protection scheme, and controlling the differential protection scheme to reactivate the differential protection.

There is provided a method of operating a reconfigurable differential protection scheme for carrying out differential protection of an electrical power network, the electrical power network comprising terminals, each of the terminals configured to be in communication with each other within a communications network. The method includes controlling the differential protection scheme to deactivate the differential protection, and selecting a terminal to be configured out of or into the differential protection scheme. The method also includes communicating reconfiguration information among the terminals, the reconfiguration information including the selection of the terminal to be configured out of or into the differential protection scheme. The method also includes modifying a respective differential protection algorithm at each of the non-selected terminals so as to configure the selected terminal out of or into the differential protection scheme, and controlling the differential protection scheme to reactivate the differential protection.

A method of identifying an arc fault in a wire operably connected between a controller and a load. The method includes operably connecting a sense wire to the wire in close proximity to a load supplied by the controller via the wire, measuring a first voltage on the wire at the load via the sense wire, measuring a second voltage on the wire at an output interface of the controller and measuring a current in the first wire. The method also includes identifying any differences between the voltage on the wire measured at the load and the second voltage on the wire measured at the output interface, ascertaining any anomalies in the current measured in the wire, and correlating the differences between the first voltage and the second voltage with any anomalies in the current to identify an arc fault.

A power system includes: a self-commutated power converter including a first arm and a second arm, each including switching elements; a first circuit breaker configured to interrupt a current flowing through a power transmission line provided between a first bus and a second bus; a first circuit breaker control unit configured to control the first circuit breaker; a converter control unit configured to stop the switching elements based on a first arm current value and a second arm current value; and a setting unit configured to set a voltage value of an AC voltage output from the power converter such that when a fault occurs in the power transmission line, the first circuit breaker is opened while the switching elements are not stopped. The converter control unit is configured to operate the switching elements such that an AC voltage with the set voltage value is output.

A differential protection method for generating a fault signal includes measuring current measurements at least at two different measuring points of a multiphase transformer for each phase. The current measurements for each phase are used to form differential current values and stabilization values. The fault signal is generated if it is determined during a trigger region check that a measurement pair of at least one of the phases, being formed by using one of the differential current values and the associated stabilization value in each case, is in a predefined trigger region. In order to be able to selectively and reliably distinguish an external fault from an internal fault, the transformer has a grounded star point and a zero system current flowing through the star point is used to form the stabilization values. A corresponding differential protection device is provided for performing the differential protection method.

A differential protection method for generating a fault signal includes measuring current measurements at least at two different measuring points of a multiphase transformer for each phase. The current measurements for each phase are used to form differential current values and stabilization values. The fault signal is generated if it is determined during a trigger region check that a measurement pair of at least one of the phases, being formed by using one of the differential current values and the associated stabilization value in each case, is in a predefined trigger region. In order to be able to selectively and reliably distinguish an external fault from an internal fault, the transformer has a grounded star point and a zero system current flowing through the star point is used to form the stabilization values. A corresponding differential protection device is provided for performing the differential protection method.